title: Beat-frequency adjustable Er3+-doped DBR fiber laser for ultrasound detection.
abstract: A compact low beat-frequency dual-polarization distributed Bragg reflector (DBR) fiber laser whose beat frequency can be varied, for high-frequency ultrasound detection has been proposed and experimentally demonstrated. The laser was fabricated in small birefringent commercial erbium-doped fiber. It operated in a robust single-longitude mode with output power of more than 1 mW and high signal-to-noise ratio better than 60 dB. Induced birefringence to the fiber during the UV inscription process is small (~10(-7)) and consequently the laser beats at a low frequency of ~20 MHz which is at least one order of magnitude smaller than previously reported results, making frequency down-conversion unnecessary. The beat frequency can be adjusted by controlling the side-exposure time of the UV light irradiating the gain cavity, providing a simple approach to multiplex a large number of DBR fiber lasers of different frequencies in series using frequency division multiplexing (FDM) technique. The proposed DBR fiber laser is also temperature insensitive, making it a good candidate for hydrophone applications.
authors.affiliation: Photonics Research Center, Department of Electrical Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong SAR, China. tuanguo@jnu.edu.cn
authors.forename: Tuan
authors.initials: T
authors.lastname: Guo
authors.forename: Allan C L
authors.initials: AC
authors.lastname: Wong
authors.forename: Wei-Sheng
authors.initials: WS
authors.lastname: Liu
authors.forename: Bai-Ou
authors.initials: BO
authors.lastname: Guan
authors.forename: Chao
authors.initials: C
authors.lastname: Lu
authors.forename: Hwa-Yaw
authors.initials: HY
authors.lastname: Tam
mesh_terms: D004867:Equipment Design; D019544:Equipment Failure Analysis; D004871:Erbium / Q000737:chemistry; D005336:Fiber Optic Technology / Q000295:instrumentation*; D007834:Lasers; D008904:Miniaturization; D012031:Refractometry / Q000295:instrumentation*; D013685:Telecommunications / Q000295:instrumentation*; D014159:Transducers; D014463:Ultrasonography / Q000295:instrumentation*
chemical_list: D004871:Erbium